The advance of computer technologies is beginning to realize functions such as association and linking of processes across networks even in office devices and general household appliances. Device control protocols such as UPnP (Universal Plug and Play), Jini®, and Jxta® are known as network technologies that implement fusion of these device controllers across networks.
UPnP will be described below as a representative example. UPnP is a device control protocol used on networks that support practical standard protocols, such as IP (Internet Protocol), TCP (Transfer Control Protocol), UDP (User Datagram Protocol), HTTP (HyperText Transfer Protocol), and XML (eXtensible Markup Language), in the Internet world.
UPnP uses SSDP (Simple Service Discover Protocol) to find a device controller connected to a network, and grasp profile information expressing the predefined specifications and settings of a device controller to be controlled. SSDP is a fundamental portion that constitutes UPnP, and IETF has issued standard specifications. UPnP uses IP broadcast to find a device it wants. For example, when “a device capable of playing back digital video streams?” is broadcast, devices matching the condition voluntarily transmit their IP addresses and host names to the inquiry source. Also, the profile information indicating the predefined specifications and settings and practical functions of a device controller to be controlled is exchanged at that time. The data format used in information exchange is XML, and the information is communicated by HTTP.
SOAP (Simple Object Access Protocol) is used to control a device. SOAP is an RPC-based Internet communication industry standard protocol that is determined in order to smoothly exchange XML Web services. SOAP is used to transmit a control message to a device and obtain a result or error. A UPnP control request is a SOAP message containing an action that calls by designating a parameter. The response is also a SOAP message and contains a status, and a value and parameter are returned.
A device control protocol (e.g., UPnP) used to interconnect devices across a network often adopts a method that exchanges the entire profile information having a predetermined structure following one predetermined profile exchanging procedure (e.g., SSDP).
For example, patent reference 1 describes that a device with low throughput can deal with large amounts of information by exchanging profile information between devices and then arranging, in a temporary save location, an area for internal processing such as document processing.
Patent reference 1: Japanese Patent Laid-Open No. 10-143420